The present invention relates to an electron gun for a color cathode ray tube, and particularly to an electron gun for a color cathode ray tube capable of realizing a high quality image.
Generally, in accordance with methods for supplying voltage to electrodes of the focusing system, an electron gun for a color cathode ray tube can be classified as either a bipotential type or a unipotential type of a single focusing system, and a uni-bipotential focusing type of a multistep focusing system. The unibipotential focusing type electron gun is advantageous in that an electron beam can be focused by multistep focusing. However, since a high voltage of about 300 to 700V is applied to the central electrode among the electrodes constituting a unipotential type electrostatic lens, the stronger auxiliary electrostatic lens cannot be formed.
In order to solve the above-described problem, this applicant has filed Korean patent application No. 90-20987 which relates to an electron gun formed as illustrated in FIG. 1.
In more detail, the proposed electron gun is formed by a sequential arrangement of a triode consisting of a cathode 2, a control electrode 3, and a screen electrode 4; a unipotential auxiliary lens consisting of first, second, and third focusing electrodes 5, 6, and 7; and an anode 8 which forms a bipotential major lens by being positioned in the vicinity of third focusing electrode 7. In the electron gun formed as the above, the middle or second focusing electrode 6 interposing between first and third focusing electrodes 5 and 7, which constitute the unipotential auxiliary lens, is connected to control electrode 3 which is supplied with a ground or negative potential Va'. First focusing electrode 5 and third focusing electrode 7 are supplied with a voltage Vc' of about 4 to 10KV, and screen electrode 4 is supplied with a voltage Vb' of about 400 to 1000V. Meanwhile, anode 8 is supplied with the highest voltage Vd' of about 20 to 30KV.
The characteristic of the electron gun having the above-stated structure is that control electrode 3 is connected to second focusing electrode 6, and then, a voltage of about 400 to 1000V is supplied, thereby forming a more intensified auxiliary lens. However, the obtained result is unsatisfactory by this structure, also.